The present invention generally relates to interior assemblies for aircraft, and more particularly to a system of sidewall panels, window assemblies, and insulation structures for installation upon a cabin wall within the interior of an aircraft.
Fabrication of a commercial aircraft typically consists of building an airframe (sometimes referred to as a primary structure or fuselage) consisting of a series of vertically oriented frames, or ribs, that encircle a cabin area for transporting personnel and cargo. The outboard side of the frames is covered with an outboard wall or skin and the inboard side of the frames in the cabin area may similarly be covered with sidewall trim panels. Along the outboard wall and between the frames, other aircraft components such as insulation, electrical conduits, ventilation ducting, control mechanisms, and the like may be installed, so that they may be enclosed between the outboard wall and the sidewall trim panels. Provisions must also be made for windows that must extend through the space between the inner and outboard walls.
The outboard wall is fixedly attached to each frame by standard means well known to the industry, such as by rivets, so that structure and rigidity is provided for the airframe, but the sidewall trim panels must be removable to allow access to these other aircraft components in the space between the sidewall and outboard wall. To facilitate removal and installation of the sidewall trim panels, elaborate systems of special fasteners, insulation supporting mechanisms, window reveals, and outer window assemblies have been devised to allow access to the aircraft components within the space. Therefore, current inner sidewall systems have been constructed piecemeal of many numerous components, and this has made installation and removal expensive in terms of number of sidewall parts and time required to remove and replace them.
In general, the inner sidewall system may include four basic components, namely, sidewall panels, window reveals, insulation between the inner sidewall and the outboard wall, and a fastening arrangement to allow each component to be installed, removed, and replaced while minimally affecting the other components. However, each component of an inner sidewall system has its own set of design issues.
The sidewall trim panels of commercial passenger aircraft are typically configured as a number of generally curved vertical panels that extend between the floor and storage bin of the aircraft in a side-to-side manner along either interior wall of the aircraft. Insulation is located behind the sidewall trim panels to reduce the amount of noise and vibration resulting from such external sources as the aircraft engines or turbulent air flow to the cabin. This noise and vibration is further reduced by mounting the sidewall trim panels against rubber shock absorbers which are also known as “shock mounts”, and which are affixed to the frames of the aircraft. However, the sidewall trim panels must be held securely against the shock mounts so that any vibration of the airframe does not cause these panels to vibrate against the frame, shock mounts, and other interior components.
In addition to these habitability factors of reduced noise and vibration, it is desirable that the panels and insulation be installed and removed easily and rapidly. This is true not only during the initial construction of the aircraft, but also later on when maintenance is being performed. A number of air conditioning ducts and electrical wiring harnesses are typically routed behind the panels, and these ducts and wiring must be accessible by removing the sidewall trim panels.
In many conventional passenger aircraft, the sidewall trim panels have tabs that extend outwardly from the vertical edges of the panels. The panels are secured by horizontal bridge fasteners which are inserted over the tabs of adjacent sidewall trim panels and which are connected to the frames via the shock mounts by screw fasteners. A decorative vertical trim strip may be inserted between the edges of the adjacent panels and over the tabs to provide a pleasing appearance to the cabin. Behind the panels are located the shock mounts that are riveted to the frame. The shock mounts include threaded receptacles for securing the bridge fasteners to the aircraft. Insulation is installed behind the sidewall panels and secured to the vertical frames of the airframe.
Since the shock mounts are conventionally prelocated by being riveted to the aircraft frames prior to attaching the panels or insulation, it is sometimes difficult to properly secure the panels to the aircraft. This is because either the tabs of the adjacent panels do not properly align with each other to permit simultaneous engagement by the bridge fasteners, or because the tabs do not align with the position of the bridge fastener; the position of the bridge fastener being fixed by the location of the mounting holes in the prelocated shock mount. Furthermore, the lengthwise gap between the edges of the adjacent panels may be too small to accommodate a vertical trim strip, or the projecting screw fasteners may prevent the trim strip from being easily inserted in the gap.
Windows are generally constructed with an outer window assembly that becomes a part of the airframe and a window reveal that is attached through a hole in a sidewall trim panel and mated to the outer window assembly. This mating of the window reveal with the outer window assembly allows the window reveal to be removed without requiring removal of the outer window assembly. Current aircraft designs include the use of different hardware fastener mechanisms for attaching a window reveal to an aircraft sidewall panel. A typical window reveal may include a dust cover and other ancillary items such as shades. The most common of these assemblies require the combination of hardware fastener mechanisms, typically brackets, gaskets, and adhesives to affix the reveal to an aircraft's fixed outboard wall or skin. The brackets are affixed, via the adhesive, to the sidewall trim panel. The window reveal is then affixed to the brackets. In other installations, the window reveal is affixed to the sidewall trim panel using both mechanical affixing and adhesive affixing. The placement of both the fasteners and the window reveal must be precise within the sidewall trim panel so that the window reveal can be easily mated up to the opposing outer window assembly when the panel and window reveal are installed. This installation of the numerous brackets can be very labor intensive and time consuming; the sidewall must first be sanded and the adhesive must then be applied and allowed to cure for an extended period, before the window reveal can be affixed to the brackets. Further installation often requires specially designed tools or locating jigs. In addition, fuel economy can be negatively affected as the brackets and adhesives add weight to the aircraft, which in turn adds to the operating cost of the aircraft. In addition, the brackets can be very pliable and weak or brittle. They may therefore be subject to increased maintenance and replacement costs.
Additionally, because there is quite a variation in affixing mechanisms between various airplane models, standardization of the window assemblies across airplane models is difficult. Difficult access to whole or part of the window assembly makes standard window maintenance, like cleaning, expensive and time consuming. This is because maintenance must be done by removing the whole window assembly or accessing the whole sidewall.
The system of fasteners and brackets must be consistently and uniformly attached to the frames and the sidewall trim panels so that they correctly align. The brackets must be precisely placed within close tolerances on the frames and outboard surface of the sidewall trim panel in a very exacting manner, so that the sidewall trim panel may be accurately aligned. To achieve these close tolerances, one of two methods is generally used; either special locating jigs must be utilized or else slots must be incorporated into the sidewall trim panel so that it can be adjusted both up/down and fore/aft for precise fit. Such methods must be used since the brackets cannot be precisely placed when they are affixed by adhesives. This alignment operation is very tedious and exacting, and it leads to significant assembly costs because installers must take substantial time and care to precisely affix and adjust the brackets.
The installation and placement of insulation within the inter-sidewall space can also be difficult and time-consuming. It is well known in the art that an insulation layer is required between the sidewall panels and the outboard wall for purposes of retaining heat within the aircraft cabin, reducing vibration, and reducing external noise. Heretofore, bats of woven insulation or bags of limp fiberglass have been affixed to the exterior wall and fuselage of the aircraft cabin and held in place with brackets and clips inserted through the insulation material, so that they may be held in place until the sidewall trim panels can be installed over the insulation materials. However, one disadvantage of this process is that the initial installation of such insulation involves extensive technician time in order to create and seal numerous penetrations in the insulation, to place the numerous brackets required for holding the insulation, and to attach the insulation to the brackets. Furthermore, the entire length of the cabin must be fitted with the insulation layer before any of the sidewall trim panels are installed. Another disadvantage is that, because of the limp nature of traditional insulation, many penetrations must be made for supporting brackets, which in turn can cause numerous gaps in the insulation. These gaps greatly diminish the ability of such insulation to reduce noise since they create flanking paths though which noise may efficiently transmitted. Still another disadvantage is that the numerous brackets increase the weight of the aircraft and must themselves be affixed to the frames and exterior wall of the fuselage, which further increases technician time. When the insulation layer must be removed for maintenance at some point along the cabin wall, the technician must again spend a significant amount of time removing and reinstalling the insulation layer.
The prior art addresses numerous aspects of the different sidewall components in isolation. For example, U.S. Pat. No. 6,227,491 discloses a modular window unit that may be affixed to an interior sidewall trim panel of an aircraft. The window unit is centered in an opening of the sidewall trim panel by means of a centering lug located at the bottom center portion of the window unit and is assisted by tabs located on each bottom corner of the window unit. The tabs serve as an axis for holding the window unit to the bottom portion of the opening in the panel and rotating the top portion into the opening, to be detachably connected there by opposing snap fastenings on either side of the upper opening. The disclosure does not discuss how the sidewall trim panels are attached to the outer wall of the aircraft, nor does it describe the details of wiring and insulation that must be operationally inserted between the outer wall and inner sidewall trim panel.
U.S. Pat. No. 4,739,955 discloses an aircraft sidewall trim panel and insulation retainer for affixing the panel to the inboard frame of an aircraft. An aircraft panel is described that is secured at its lower side to a longitudinal dado panel running the length of the cabin and at its upper edge to an upper fixed portion of the cabin structure, such as a longitudinally extending row of storage bins. The panel is made of a resilient bendable material that is flexed against special shock absorbing retainers by the upper and lower edges of the panels. The retainers maintain the panel at a spaced distance from the aircraft frame members by use of an elastometric plug held by the retainer against the outer panel surface, in order to prevent vibration of the sidewall panel. The retainer also holds bats of insulation in place between the panel and the outer wall of the aircraft.
Thus, there exists a need to provide a system and method of configuring an aircraft interior sidewall that may be easily installed and removed for maintenance without requiring excessive time or equipment. There is also a need for a sidewall that allows aircraft components between the interior sidewall and the exterior sidewall to be accessed without having to remove an excessive number of adjacent aircraft components from their installed position. Finally there is a need for a system of sidewall panels, insulation, window assemblies and supporting brackets that minimizes gaps and effectively controls noise transmission.